Current methods used to manage stage 3 to stage 4 chronic kidney disease patients typically involve monitoring the patient's symptoms and glomerular filtration rate (GFR). Prior to the patient reaching a point where additional therapy in the form of supplemental hemodialysis is needed, an access point (fistula) will typically be created by surgically diverting an artery to a vein. The fistula usually takes four to six weeks to mature, but can take up to six months to mature and be ready for hemodialysis. In some situations, the patient's kidneys decline to rapidly such that the fistula has not matured before they require dialysis treatment. In such situations, a central venous catheter may be used until the fistula matures. However, central venous catheters are more infection prone and suffer from clotting and fatigue issues. Accordingly, it is desired to ensure that the fistula matures prior to the patient requiring hemodialysis. Unfortunately, it can be difficult to predict when a stage 3 or stage 4 chronic kidney disease patient will need supplemental hemodialysis treatment and current methods for sufficiently monitoring such patients are lacking.
Once a patient begins undergoing dialysis treatment or another fluid removal processes, such as ultrafiltration, it can be difficult to determine how much fluid to remove during a given treatment session. The amount of fluid to be removed is determined before the treatment session and is related to the patient's pre-treatment weight, fluid addition during treatment and their theoretical dry weight. However, it can be difficult to accurately determine a patient's dry weight, which is considered to be the weight that the person would be if their kidneys were properly functioning. What a given patient might weigh if their kidneys were properly functioning is often an unknown variable and can change over time. Yet an accurate determination of the patient's dry weight is important to the successful outcome of a fluid removal session.
Unfortunately, the patient's dry weight is not typically calculated or re-evaluated frequently. Unlike the patient's actual weight, which is measured before and after a fluid removal session, dry weight is often determined much less frequently; e.g. monthly, and much can change in the time between a dry weight determination and a given fluid removal session, which typically occurs three times a week. While being an important variable in fluid removal considerations, dry weight is often difficult to calculate and may vary between sessions.
Errors in fluid volume removal can result in severe hypotension and patient crashing following or during hemodialysis treatment, and insufficient frequency of fluid removal sessions can have serious consequences. For example, sudden and cardiac death (including death from congestive heart failure, myocardial infarction, and sudden death) are common in hemodialysis patients. See Bleyer et al, “Sudden and cardiac death rated in hemodialysis patients,” Kidney International, (1999), 55:1552-1559.
For various reasons, additional monitoring of patients for which a blood fluid removal session is indicated may be desired.